應用於粉凝式3D列印機之電磁致動噴頭的設計與實作

Abstract

本論文主要討論液滴成形噴頭的設計，目標為應用在生醫領域等液滴不適合發熱或過度變形的粉凝式3D列印機中，依照液滴成形方法的差異，主要設計了兩種型式，第一種型式採用連續式液柱噴頭，搭配截水式機構，以截斷水柱的方式產生液滴，第二種設計應用電磁致動器，藉由高頻沖壓的方式，以適當的方式推擠針筒內的液體以液滴形式噴出，為了驗證各種液滴噴頭設計的效果，文中安排實驗與模擬，檢驗各項參數對液滴產生之影響。

本研究為驗證兩種液滴噴頭的效果，以硫酸鈣粉末逐層噴灑液滴後形成的3D實物造型，檢驗噴頭的效果與實用性，疊層列印實驗中，截水式機構產生的液滴尺寸相對較大，其單層的粉凝厚度超過鋪層厚度1mm，因此下層的凝塊會產生1.5mm的尺寸誤差，電磁致動式液滴噴頭部分，其產生的液滴尺寸相對較小，可獲得較好的凝塊尺寸，若單層的粉凝厚度小於鋪層厚度，層與層的黏著力較差，適當調整鋪層厚度可獲得較佳的疊層黏著強度。

研究中應用ANSYS/FLUENT模擬各種噴頭流固耦合形成液滴的作動過程與結果，除了模擬設計的兩種噴頭，另外增加工業用點膠噴頭的模擬，模擬的目的在於建構噴頭的數值模型，並提供實驗中選用噴頭驅動參數時的一個參考，觀察三種噴頭的模擬結果，截水式機構與電磁致動式液滴噴頭的模擬可與實驗值保有一定的趨勢性。

針對液滴的實驗值，比較設計的噴頭與工業用點膠噴頭，電磁致動式液滴噴頭可產生相對較小的液滴尺寸(直徑約0.3mm)，同時具有較快的液滴生成速率，其液滴的生成效能是三種噴頭中較佳的，不過穩定性較其他兩種噴頭差。

本研究提出了兩種液滴噴頭的設計概念，在致動方法上，兩種設計皆可避免生物材料在噴擠的過程產生變質，以目前的實驗結果而言，電磁致動式噴頭的液滴生成效能較好，是未來可繼續發展的部分。

This paper proposed the design and evaluation process of a droplet generator which was applied in plaster-based 3D printing. The proposed 3D printing machine is designed for bio-medical applications, especially of the cases that liquid fluid cannot be heated or deformed dramatically during droplet creation. Two types of water droplet generator were presented in the study. The first type was combining the liquid jet nozzle with water column cutoff mechanism to form a water droplet. While for the second type, the water droplet is generated under the process of squeezing the water column through the syringe by using electromagnetic actuator. Experiments and simulations were arranged in this study to verify the parameters effect on droplet formation.

In the study, three different kinds of droplet generator model are considered and simulated using ANSYS/FLUENT fluid dynamic simulation software. The purpose of the simulation is to establish the numerical model of droplet generator, and the simulation results can be helpful in choosing feasible actuating parameters for the experiments. As checking the simulation results, both of the water column cutoff mechanism and electromagnetic actuated droplet generator play a better performance in matching the experiment results.

As comparing the efficiency of three types of droplet generator, electromagnetic actuated droplet generator can create smaller droplet (about 0.3mm) with faster speed. While the current performance of droplet size forming stability of electromagnetic actuated droplet generator need to be improved in the future study.